The present invention relates generally to a saver sub and a system and a method for using a saver sub in a drilling system.
FIG. 1 illustrates a typical drilling system 300 for use in drilling to recover oil and gas deposits within the Earth. The system 300 is a land-based rig, however, the principles and equipment described herein may also apply to an off-shore rig used to drill into the Earth's crust beneath the ocean or other body of water. The system 300 includes a rig 301 from which a drill string 304 is suspended into a wellbore 302. A drill bit 306 at the lower end of the drill string 304 is used to drill the wellbore 302. The surface systems may include a hook 312 for suspending at least a portion of the weight of the drill string 304, as well as a rotary swivel 314, which allows the drill string to rotate relative to the hook 312. A rotary table 308 may be used to rotate the drill string 304. Another system to rotate the drill string 304 is called a “top drive” system, which may be used instead of a rotary table.
The drill string 304 is typically comprised of several sections of drillpipe 338 connected together, end-to-end, to form the drill string 304. At the lower end, the drill string 304 includes a bottom hole assembly (“BHA”) 326 and a drill bit 306. The BHA 326 comprises sensors and other equipment for collecting data related to the direction and inclination of the bottom hole assembly, pressure and temperature data, and formation property data, such as porosity, permeability, resistivity, density, hydrogen content, and other downhole properties. The sensors may be part of measurement-while-drilling (“MWD”) or logging-while-drilling (“LWD”) tools utilized in the BHA 326.
The system 300 also includes a surface computer 332 which may be used for any number of purposes. For example, the surface computer 332 may be used to store and/or interpret signals received from the BHA 326 or to control the rig. Reliably conveying data and/or power along a drill string has become an increasingly important aspect of wellbore drilling operations.
Numerous types of telemetry systems are commonly used in connection with MWD and LWD systems to communicate with the surface computer 332. For example, mud-pulse telemetry systems use modulated acoustic waves in the drilling fluid to convey data or information between the BHA 326 and the surface computer 332. However, mud-pulse telemetry systems have a relatively low data transmission rate of about 0.5-12 bits/second and, thus, substantially limit the amount of information that can be conveyed in real-time and, as a result, limit the ability of an oil company to optimize their drilling operations in real-time. Other telemetry systems such as electromagnetic telemetry (EM) via subsurface earth pathways and acoustic telemetry through drill pipe have been employed. These other telemetry systems also provide a relatively low data rate that may limit the ability of an oil company to employ sophisticated real-time data processing to optimize its drilling operations.
Wired drill pipe is an emerging technology that may be used to provide communication and power distribution to the BHA 326 and throughout the drilling system. For example, wired drill pipe may be used to transmit data from a measuring device in the BHA 326 to the surface computer 332. In other examples, wired drill pipe may be used to transmit data or instructions from an uphole system to the BHA 326. In addition, wired drill pipe may provide communications to and from sensors or other electronics positioned at points along the drill string.
In contrast to mud-pulse and electromagnetic telemetry systems, a wired drill pipe system can convey data at a relatively high rate along the length of a drill string. One example of a wired drill pipe system 200 is shown in FIG. 2, which illustrates three interconnected pipe sections 201a, 201b, 201c. The upper pipe section 201a is connected to the center pipe section 201c by mating the pin end 221a of the upper section 201a with the box end 210c of the center pipe section 201c. Likewise, the center pipe section 201c is connected with the lower pipe section 201b by mating the pin section 220 of the center pipe section 201c with the box end 210b of the lower pipe section 201b. In this manner, the drill string 104 may be created by mating adjacent sections of the drillpipe 138.
The center section 201c includes a communicative coupler 211 in the box end 210c of the pipe section 201c. When the upper pipe section 201a and the center pipe section 201c are connected, the communicative coupler 211 in the center pipe section 201c is located proximate a communicative coupler 221a in the box end 220a of the upper pipe section 201a. Likewise, a communicative coupler 221 in the pin end 220 of the center pipe section 201c may be proximate a communicative coupler 211b in the box end 210b of the lower pipe section 201b. 
A wire 202 in the center pipe section 201c spans the length of the pipe section 201c and is connected to each communication coupler 211, 221. Accordingly, data and/or power transferred to from pipe section 201a and 201b may be transmitted through the wire to the communicative coupler 211, 221 at the opposing end of the pipe section 201a, 201b, where it may then be transferred to the next adjacent pipe section. The communicative couplers 211, 221 may be any type of couplers that enable the transfer of data and/or power between pipe sections. Such couplers include direct or galvanic contacts, inductive couplers, current couplers, and optical couplers, among others.
One example of a wired drill pipe is disclosed in U.S. Pat. No. 3,696,332, issued to Dickson, Jr., et al., which discloses a drill pipe with insulated contact rings positioned in a shoulder at both ends of the pipe. The contact rings in a single segment of pipe are connected by a conductor wire that spans the length of the pipe. When a segment of drill pipe is made up with an adjoining segment of pipe, the contact ring in the first segment of pipe makes contact with a corresponding contact in the adjacent pipe section.
When a wired drill pipe system is used, it is necessary to have a communication link between the topmost wired drill pipe and the surface computer 132 (which, inter alia, typically performs one or more of the following functions: receiving and/or sending data, logging information, and/or control information to and/or from downhole and surface equipment, performing computations and analyses, and communicating with operators and with remote locations). However, with existing techniques, the top drive system must be modified or special subs must be included in the drill string and such changes can significantly hinder normal drilling operations.
The present invention, therefore, provides an improved saver sub that may be secured to a drill string, whether wired or non-wired, to improve drilling operations. The saver sub may house electronics, one or more power sources, and/or one or more antennas for transferring data to the surface computer or other data processing or storing system.